eth/downloader: abort sync if master drops (timeout prev) #2868
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Updated: Mon Aug 8 08:42:29 UTC 2016 |
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👍 General observation: maybe the cancel channel should be passed into fetchHeight, fetchAncestor, ... to guard against races. They all read from d.cancel without synchronisation which might be OK but it's safer to just pass the channel around. |
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LGTM 👍 |
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Currently the downloader tracks peer drops for "data downloads", so that if a remote node is disconnected, all its assigned fetches are returned into the queue to be pulled by someone else.
However fetching the remote height; fetching the common ancestor and fetching the skeleton chain are done outside of the "fetch queue", so none of these code segments are aware that a peer was dropped. This results in them having to wait for a timeout to hit before aborting and starting over. Given the EDGE release's bumped timeout of 1 minute, this can stall sync quite a lot.
This PR adds a minor polish to the downloader so that for every sync cycle it maintains the master peer that it wants to sync with. Subsequently if the master peer is dropped, the sync cycle is cancelled in its entirety.